Flexible circuit configurations are advantageous, inter alia, for use in applications in which the circuit configuration must have permanent flexible properties, in particular, for example, in body implants or in objects which have at least limited flexibility in use, such as credit cards.
Flexible circuit configurations contain at least one insulating layer and at least one conductive layer, at least the conductive layer being structured in the surface. The terms insulating layer and conductive layer refer in this case and hereafter to the electrical properties of the layer materials. Frequently, at least two structured conductive layers are provided, which are spaced apart from one another by at least one insulating layer acting as a separation layer. The two conductive layers are typically conductively connected to one another in spots via through contacts through the separation layer, which is also structured in the surface for this purpose, so that a three-dimensional configuration of conductor structures arises. The structuring of the conductive layers and the insulating layers is typically performed by photolithography using different masks.
For a high precision during the structuring of a layer deposited over the entire surface, which is important in particular in the case of very small structure dimensions, the layer structure can be deposited on a rigid substrate, for example, on a silicon wafer. After the layer structure is deposited, optionally after further method steps of the production including possible equipment with discrete components on a surface of the flexible circuit configuration, the flexible circuit configuration is separated from the substrate. Since the layer structure itself is typically less than 0.1 mm thick, a flexible film can be connected to the layer structure, which can also have through contacts. The rigid substrate advantageously allows the handling of the circuit configuration during the production process, however, the separation from the substrate can result in damage of the finished flexible circuit configuration because of sensitivity of the layer structure to various typical detachment methods.